Offset axles are known already, one embodiment having been described in German Patent 30 27 806. In offset axles, the axle shafts are offset relative to the wheel axes by a specific distance, the so-called gantry height or depth. This offset is created by an intermediate gear, the so-called gantry drive, directly on the wheel drive. An upward axle offset makes greater vehicle ground clearance possible, and a downwards offset makes possible a lower platform level. In local-traffic or town buses, the lowest platform level is desirable in order to make it possible for the passengers to get on and off comfortably and easily. The passengers can enter the bus from the curb without having to climb perceptibly. This is a significant help, especially for wheelchair users or perambulators.
In German Patent 30 27 806 an offset axle for local-traffic buses is described. In the offset axle, a differential is eccentrically placed directly next to one of the two gantry drives. In that case, the differential requires space and the inner bulkhead of the vehicle must, therefore, be increased in this place. In order that the aisle on the lower platform level remains sufficiently wide, the differential must be lodged, as close as possible, to one of the wheel wells and thus also as close as possible to one of the gantry drives. The axle shafts of the differential are each inserted into a drive pinion of the gantry drive which is freely mounted in a self-centering manner directly between two intermediate pinions and in contact with them so that all three pinion axes lie in one plane. The intermediate pinions, in turn, mesh with a spur wheel for driving the wheels. The force of the meshing of teeth and the input are uniformly divided between the two intermediate pinions. This design of the offset axle is smooth running and compact in height and an axial expansion and thus allows a wider aisle in the platform and sufficient ground clearance despite a larger gantry depth. The gantry drive is greatly geared down in order that the maximum torque of the axle shafts and the size of the differential can be kept small. The axle shafts are in the center of axle bridge housing which, as a consequence of the needed power, has a cross section clearly larger than that of the axle shafts.
The offset axle described in German Patent 30 27 806 has the disadvantage that because of the space needed by the gantry drive, no commercially available disc brake can be integrated in the axle system without the platform height clearly and intolerably increasing as result of the necessary constructional change. In that case, the spur wheel has to be significantly reduced to drive the wheel to be able to locate the disc brake. The drive pinion must be equally reduced in order to maintain the reduction ratio. Thus the gantry depth diminishes and the platform level increases. Besides, as a result of the axial length of the brake cylinders, the aisle width of the platform further diminishes in the area of the axle of the vehicle.